Cryptococcus neoformans, the main causative agent of cryptococcosis, is a fungal pathogen that causes life- threatening meningoencephalitis in immune compromised hosts. Current anti-cryptococcal drug therapies are oftentimes rendered ineffective due to drug toxicity, the emergence of drug resistant organisms, and/or the inability of the host's suppressed immune system to aid in resolution of the disease. To date, there is no vaccine or immunotherapy approved for the treatment of cryptococcosis. Experimental efforts to immunize mice using various protein preparations or serum therapy using anti-cryptococcal monoclonal antibodies have thus far induced only partial protection against subsequent challenge. Studies in our laboratory have shown that an acute infection with a C. neoformans strain H99 engineered to express IFN-3, designated C. neoformans strain H993, results in the induction of potent CD4+ Th1-type cell-mediated immune responses and resolution of infection. Moreover, immunization with C. neoformans strain H993, but not heat-killed C. neoformans, results in sterilizing immunity against a subsequent lethal pulmonary challenge with wild-type cryptococci in immune competent and CD4+ T cell deficient mice. These studies suggest that a vaccine strategy to induce protective anti-C. neoformans immunity in immune compromised hosts is indeed achievable. Accordingly, we have sought to identify cryptococcal protein candidates that may be used as part of a subunit vaccine to induce protective CD4+ Th1-type cell-mediated immunity (CMI) against cryptococcosis in mice. Consequently, the studies proposed herein use a combined proteomic and immunological approach to screen complex mixtures of cryptococcal proteins for those proteins that elicit antigen-specific Th1-type cell-mediated immune responses against C. neoformans infection using the following Specific Aims: (1) To identify and characterize C. neoformans proteins that induce protective Th1-type cell-mediated immune responses. (2) To evaluate the efficacy of C. neoformans proteins to induce protection against experimental pulmonary cryptococcosis. PUBLIC HEALTH RELEVANCE: Cryptococcus neoformans is an opportunistic fungus that may cause life- threatening infections of the brain in individuals with suppressed immune systems. I am proposing to perform studies to identify and evaluate the efficacy of specific C. neoformans proteins to induce protection against cryptococcal infections. My expectation is that these studies will lead to the development of therapies and/or vaccines to treat or prevent fungal infections.